Once the MFS is complete, it can be added to any file. There are several options for installing the MFS. Each offers slightly different capabilities.
Developers can install any number of MFSs onto a file, and can mix their own MFSs with system MFSs such as SI.MFS and QUICKDEX.MFS. Some MFSs, however, are sensitive to the sequence in which they are called. For example, SI.MFS absorbs several BFS calls in their entirety, and does not pass them on to the next MFS or to the BFS.
Because of this, developers need to be aware of the effect of other MFSs that precede or follow their own MFS, and place their MFS accordingly.
Manual MFS Installation
If intended to be a permanent addition to the file, the MFS is installed by adding its name to the media map (REVMEDIA) entry for the file. A manual installation consists of updating the media map entry for a file with the MFS name, and (re)attaching the file. After the file has been attached, the MFS will be called for all access to the file. To install an MFS manually, follow the instructions listed below.
Because it requires that the REVMEDIA file be attached, the manual installation procedure can only be performed from the SYSPROG account. However, this procedure can be performed to install an MFS onto a file that belongs to any account.
Attach target media map. Determine the volume name for the file onto which the MFS is to be installed. For example, if the file is on the default directory, the volume name is DATAVOL. Attach the media map for the volume by entering the ATTACH_TABLE command using the System Monitor. For DATAVOL, the output is shown below:
2. Edit media map entry for file. Once the REVMEDIA file is attached, its records can be edited in the System Editor, just like records in other OpenInsight files. Records in the REVMEDIA file have a two-part key (filename*applicationname). The REVMEDIA record for the CUSTOMERS table in the EXAMPLES application, before installing SIMPLE_MFS, is shown below:
